The present invention relates broadly to the removal of sulfur oxides from a gas stream. More specifically the invention pertains to a gas treatment apparatus suitable for the removal of both sulfur oxides and dust, e.g. fly ash, from a gas stream wherein essentially no solid sulfur containing by-products are formed.
There are many methods known for the removal of sulfur oxides and dust from gas streams, e.g. power plant stack gases. A summary of these methods is given by A. V. Slack in "Removing SO.sub.2 from Stack Gases", Environmental Science & Technology, Vol. 7, No. 2, p. 110-119 (February, 1973). However, associated with these methods is the problem of disposal of the sulfate and sulfite-containing compounds formed as by-products of the gas purification method. For example, sludge disposal difficulties are discussed in an article in Chemical Week, Dec. 12, 1973, p. 45, entitled "Sludges Mire Stack-Gas Cleaning". The sludge disposal problem is of increasing economic significance and, accordingly, a method of purifying stack gas without forming solid sulfur containing by-product, e.g. sulfates and sulfites, would be very useful.
Another problem in the treatment of stack gases is the presence of dust, i.e. particulate matter, along with gaseous impurities in the gas stream. A dust-containing stream may require, in addition to a gas scrubber to remove gaseous impurities, the use of an electrostatic precipitator or a second scrubber to remove the dust particles, particularly if the dust particles are relatively small. It would be desirable to remove both dust and gaseous impurities within one contacting device.